UCC5641PW28

Overview

The UCC5641PW28 is a low-voltage differential (LVD) active terminator for SCSI networks, housed in a 28-pin TSSOP package. It operates within a supply voltage range of 2.7 V to 5.25 V and supports temperatures from 0°C to 70°C. The device provides a differential impedance of 105 Ω and a common-mode impedance of 150 Ω. It features a 1.25-V regulator with source/sink currents up to 100 mA and a 1.3-V regulator for the DIFSENS line. The output leakage current is limited to 400 nA when disconnected.

Feature Summary

• Complies with SPI-2 Ultra2, SPI-3 Ultra3/Ultra160, and SPI-4 Ultra320 standards
• Automatically detects and disconnects from single-ended or high-voltage differential buses
• Provides minimal bus loading with 3 pF output capacitance per line
• Includes integrated differential failsafe bias and reversed disconnect polarity protection

Applications

• Low-voltage differential SCSI bus termination
• System migration paths for improving SCSI standards
• High-speed peripheral interconnects requiring strict capacitance balancing

Procurement Notes

Verify the specific ordering suffix against the manufacturer's documentation to confirm the package type and tape-and-reel availability. Ensure that the procurement channel sources directly from authorized distributors to guarantee component authenticity and traceability. Cross-reference the part number with the latest datasheet revisions to confirm compatibility with your design requirements.

Selection Notes

Select this component specifically for LVD-only SCSI environments where compliance with Fast-40, Fast-80, or Fast-160 specifications is required. It is unsuitable for single-ended or high-voltage differential systems due to its automatic disconnection feature. Consider the 24-pin variant if board space constraints necessitate a smaller footprint while maintaining identical electrical performance.

Part Context

This device belongs to the UCC5641 family of active terminators designed by Texas Instruments. The family includes both 24-pin and 28-pin variants to accommodate different layout densities. These components are engineered to replace passive termination networks, offering dynamic mode detection and reduced system cost while maintaining signal integrity across various SCSI generations.

Replacement Considerations

UC5641PW28

FAQ

How does the UCC5641 handle incompatible bus drivers?

The device monitors the DIFFSENS line voltage. If it detects single-ended or high-voltage differential drivers, it automatically enters a high-impedance state, effectively disconnecting the terminator from the bus.

What are the recommended decoupling capacitors for the UCC5641?

A 4.7-µF capacitor and a 0.01-µF high-frequency, low ESR capacitor should be installed as close as possible to the TRMPWR and REG pins.

Can the UCC5641 be used in High Voltage Differential (HVD) systems?

No, the UCC5641 is designed exclusively for Low Voltage Differential (LVD) systems. In HVD systems, it will detect the presence of HVD drivers and disconnect itself.